This invention relates to a marine propulsion system, and more particularly to a driveshaft housing structure for interposition between the powerhead and lower unit of an outboard marine propulsion system.
An outboard marine propulsion system generally includes a powerhead for providing rotary power to a driveshaft. The driveshaft provides rotary power to a gearcase, or lower unit, within which a propeller shaft is mounted. A propeller is fixed to the propeller shaft, and a reversing transmission is provided in the gearcase for driving the propeller, through the propeller shaft, in either a forward or reverse direction.
A driveshaft housing is located between the powerhead and the gearcase. In the prior art, an adaptor plate is mounted to the upper end of the driveshaft housing, and the powerhead is mounted to the upper surface of the adaptor plate. The adaptor plate must be physically secured to the upper end of the driveshaft housing, such as by bolts or the like, and a gasket is located between the driveshaft housing and the adaptor plate to provide a water-tight seal. As can be appreciated, this construction entails several separate components which must be assembled together.
The present invention has as its object to provide a unitary one-piece structure for interposition between the powerhead and the gearcase of an outboard marine propulsion system. It is a further object of the invention to provide a unitary one-piece structure which includes a passage for accommodating the driveshaft, an exhaust passage for routing exhaust downwardly from the powerhead, a cooling water intake conduit for passing cooling water upwardly from the gearcase toward the powerhead, and an idle exhaust relief system for discharging exhaust during idle operation of the engine.
The invention is employed in a marine propulsion system including a powerhead and a gearcase, with the powerhead including an internal combustion engine having a rotatable output member, a cooling water inlet and an exhaust discharge. The gearcase includes a housing, a propeller rotatably mounted to the housing, and a rotatable power transfer arrangement disposed within the housing and interconnected with the propeller. A driveshaft is interposed between the rotatable engine output member and the gearcase power transfer arrangement for rotatably driving the propeller in response to operation of the engine.
The invention broadly provides an integral one-piece structure adapted for interposition between the powerhead and the gearcase, and includes an upper horizontal mounting surface to which the powerhead is mounted. An exhaust opening is formed in the upper horizontal surface, and is in communication with the engine exhaust discharge. The gearcase is mounted to a lower substantially horizontal mounting surface, and an external housing extends between the upper and lower horizontal mounting surfaces. The housing includes walls defining a longitudinally extending internal cavity. First closed wall structure is located within the internal cavity, and defines a downwardly extending exhaust passage in communication with the upper surface exhaust opening. Second closed wall structure is located within the internal cavity, and defines a substantially vertical driveshaft passage extending between the upper surface and the lower surface, to accommodate the driveshaft.
In accordance with one aspect of the invention, an idle exhaust relief system is located within the internal cavity below the upper horizontal mounting surface. The idle exhaust relief system includes at least one enclosed chamber, with the upper extent of the chamber being defined in part by one or more walls extending transverse to the longitudinal axis of the internal cavity. An idle exhaust discharge outlet is formed in one of the housing walls in communication with the exhaust idle relief chamber, and an idle exhaust passage is formed in the first closed wall structure to discharge exhaust into the chamber during idle operation of the engine. The upper surface, the lower surface, the housing, the first and second closed wall structures and the transverse walls defining the upper extent of the idle exhaust relief chamber comprise a unitary integrally formed structure. In a preferred embodiment a pair of idle exhaust relief chambers are provided below the upper horizontal mounting surface. The upper extent of one of the chambers is defined by a portion of the first closed wall structure which extends transverse to the longitudinal axis of the internal cavity, to define a bend in the exhaust passage. The upper extent of the second idle exhaust chamber is defined by a horizontal wall located below the upper horizontal mounting surface.
In accordance with another aspect of the invention, a cooling water tube is located within the internal cavity for routing cooling water upwardly toward the powerhead. The upper surface, the lower surface, the housing, the first and second closed wall structures, and the cooling water tube comprise a unitary integrally formed structure. A cooling water supply cavity opens onto the upper horizontal mounting surface, and is in communication with the engine cooling water inlet, and the cooling water tube supplies cooling water to the cooling water supply cavity. A cooling water chamber is interposed between the cooling water cavity and the discharge of the cooling water tube. The cooling water chamber is defined in part by a pair of spaced walls oriented transverse to the longitudinal axis of the internal cavity, and a passage is formed in an upper one of the spaced walls to establish communication between the cooling water chamber and the cooling water supply cavity. In a preferred embodiment, a portion of the first wall structure defines a wall of either or both the cooling water supply cavity and the cooling water chamber.
In accordance with another aspect of the invention, the downwardly extending exhaust passage, which is defined by the first closed wall structure located within the internal cavity, extends between the upper surface exhaust opening and an exhaust discharge opening formed in the lower surface. The exhaust passage includes a bend between the upper surface exhaust opening and the lower surface exhaust discharge opening. The upper surface, the lower surface, the housing, and the first and second closed wall structures comprise a unitary integrally formed structure. A third wall structure defines a water discharge passage for routing cooling water discharged from the engine downwardly through the internal cavity and into the gearcase, and includes an inlet for receiving cooling water from the internal cavity. The third wall structure comprises a part of the unitary integrally formed structure. A lower portion of the first closed wall structure defines a substantially vertical lower portion of the exhaust passage, and the lower portion of the exhaust passage communicates through the bend with an upper angled portion which extends along an axis non-parallel to the vertical lower portion. The inlet to the water discharge passage faces upwardly, and the upper portion of the first closed wall structure is located in vertical alignment with the inlet to the water discharge passage. Cooling water discharged from the engine is collected in the internal cavity so as to at least partially surround the lower portion of the first closed wall structure, to cool the first closed wall structure. A gap is provided between at least a portion of the first closed wall structure and the third closed wall structure, so that water collected within the internal cavity contacts the first wall structure at the gap. A portion of the third wall structure is preferably defined by a wall of the external housing.
In a particularly preferred form of the invention, the above-noted aspects of the invention are combined into a single structure, to provide a particularly advantageous internal arrangement to the unitary one-piece structure.
The invention further contemplates a method of making a driveshaft housing structure for interposition between the powerhead and gearcase of a marine propulsion system, substantially in accordance with the foregoing summary.
Various other features, objects and advantages of the invention will be made apparent from the following description taken together with the drawings.